Data and updating

Access and use

The data and resulting data products (tables, figures and maps) available on the indicator web pages can be used freely given that the source is cited. The indicator should be cited as following: 

HELCOM (2018) White-tailed sea eagle productivity. HELCOM core indicator report. Online. [Date Viewed], [Web link].

ISSN: 2343-2543



Result: White-tailed sea eagle productivity


Results in this core indicator report are based on data from the following time series: Denmark 1995-2016, Estonia 2002-2016. Finland 1990–2014, Germany – Federal State Mecklenburg-Western Pomerania 1973–2016, Latvia 1992-2016, Lithuania 2001-2014, Russia 1993-2014, Sweden 1964-2014/2015, Poland 2007-2016.

Spatial coverage includes the whole HELCOM Convention area although there are large differences in the size of national eagle populations (see Monitoring table 1). 

The new reporting format discriminates between controls of climbed nests and nests that have been observed only from ground level, in order to allow for calculations of a correction factor based on the data for each national population/sub-area. The correction factor relates to nestling brood size for nests that has been checked only from ground level and is needed for correct estimates of productivity for such nests (see also Description of optimal monitoring).

Strengths and weaknesses of data

Minimum detectable yearly trend (%) for a 10-year monitoring period, at a statistical power of 80%, has been estimated for Swedish data for different sample sizes, based on random sampling from data collected during 1991–2006 (Helander et al. 2008). Minimum detectable trends based on the raw dataset between 1991–2006 (with a varying annual number of observations) was 1.3% for brood size (Baltic Proper), 2.0% for breeding success (Gulf of Bothnia) and 3.0% for productivity (Gulf of Bothnia). The national survey methods are very similar but population size and thus sample sizes vary between the Contracting Parties.


 Data source

In most countries the monitoring and handling of data is carried out on a voluntary basis, often in national projects with devoted members. National data have been submitted from the contracting parties to the Swedish Museum of Natural History for storage and compilation of results in uniform format. The following are examples of national monitoring performance and data handling:

Denmark: Monitoring and data storage is carried out on a voluntary basis within the national project "Örn" under the Danish Ornithological Society.

Estonia: Monitoring and data storage is carried out on a voluntary basis by the national "Eagle Club".

Finland: Surveys of breeding populations and reproduction, ringing of nestlings and sampling are carried out by voluntary members of WWF Finland's White-tailed Sea Eagle working group. Data are stored in a competent database. Specimens found dead, DNA-samples from nestlings as well as addled eggs are stored in the Finnish Museum of Natural History, University of Helsinki.

Germany: In Western Pomerania, data are collected by voluntary ornithologists, coordinated by the "Project group for large bird species" under the auspices of the Agency for Environment, Nature Conservation and Geology. The country-wide white-tailed sea eagle data are compiled by Peter Hauff, who submits the annual reports to the mentioned governmental agency.

Sweden: Surveys of breeding populations and reproduction with sampling, sample preparation, storage in specimen bank, and evaluation and storage of data are carried out by the Department of Environmental Research and Monitoring at the Swedish Museum of Natural History, Stockholm, and are commissioned by the national EPA. Surveys of breeding populations and reproduction of reference freshwater populations have thus far been carried out by the Swedish Society for Nature Conservation ("Project Sea Eagle"). Chemical analysis is carried out at the Institute of Applied Environmental Research at Stockholm University.